1100 gamma ray bursts a day on Earth!

[pErvinalia]

In addition, chaos theory comes into play in complex systems like the brain, even if we stick to totally classical physics. A tiny difference in the firing of a single neuron could, if the system is on the edge of chaos, make large and essentially unpredictable change in the system output.

I've finally decided to read James Gleik's Chaos book. Isn't it the case that chaos is still a deterministic system, it's just that the interactions are so complex (most non-linear) that prediction is incredibly difficult. But theoretically with perfect knowledge and massive computing power, we could accurately predict the weather, say, out to the limits of that computing power. Isn't that the case?

[Xamonas Chegwé]

In addition, chaos theory comes into play in complex systems like the brain, even if we stick to totally classical physics. A tiny difference in the firing of a single neuron could, if the system is on the edge of chaos, make large and essentially unpredictable change in the system output.

I've finally decided to read James Gleik's Chaos book. Isn't it the case that chaos is still a deterministic system, it's just that the interactions are so complex (most non-linear) that prediction is incredibly difficult. But theoretically with perfect knowledge and massive computing power, we could accurately predict the weather, say, out to the limits of that computing power. Isn't that the case?

No. It's more that the sensitivity to initial conditions in even a relatively simple chaotic system is so extreme that no amount of computing power could ever predict it, even though it is governed by fully understood mathematical processes. For instance, double pendulums. The mathematical model only applies to an idealised pendulum. Its sensitivity is so extreme that the motion of a real pendulum cannot be predicted beyond the first few swings.

[JimC]

In addition, chaos theory comes into play in complex systems like the brain, even if we stick to totally classical physics. A tiny difference in the firing of a single neuron could, if the system is on the edge of chaos, make large and essentially unpredictable change in the system output.

I've finally decided to read James Gleik's Chaos book. Isn't it the case that chaos is still a deterministic system, it's just that the interactions are so complex (most non-linear) that prediction is incredibly difficult. But theoretically with perfect knowledge and massive computing power, we could accurately predict the weather, say, out to the limits of that computing power. Isn't that the case?

No. It's more that the sensitivity to initial conditions in even a relatively simple chaotic system is so extreme that no amount of computing power could ever predict it, even though it is governed by fully understood mathematical processes. For instance, double pendulums. The mathematical model only applies to an idealised pendulum. Its sensitivity is so extreme that the motion of a real pendulum cannot be predicted beyond the first few swings.

And definitely read the book - it's excellent. Using it as a guide, I managed to set up an Excel sheet on the logistic equation, and generated chaotic graphs! Was cool!

[Xamonas Chegwé]

In addition, chaos theory comes into play in complex systems like the brain, even if we stick to totally classical physics. A tiny difference in the firing of a single neuron could, if the system is on the edge of chaos, make large and essentially unpredictable change in the system output.

I've finally decided to read James Gleik's Chaos book. Isn't it the case that chaos is still a deterministic system, it's just that the interactions are so complex (most non-linear) that prediction is incredibly difficult. But theoretically with perfect knowledge and massive computing power, we could accurately predict the weather, say, out to the limits of that computing power. Isn't that the case?

No. It's more that the sensitivity to initial conditions in even a relatively simple chaotic system is so extreme that no amount of computing power could ever predict it, even though it is governed by fully understood mathematical processes. For instance, double pendulums. The mathematical model only applies to an idealised pendulum. Its sensitivity is so extreme that the motion of a real pendulum cannot be predicted beyond the first few swings.

And definitely read the book - it's excellent. Using it as a guide, I managed to set up an Excel sheet on the logistic equation, and generated chaotic graphs! Was cool!

Surely it is far easier to generate chaotic graphs by asking 12 year olds to plot y=x2?

[pErvinalia]

In addition, chaos theory comes into play in complex systems like the brain, even if we stick to totally classical physics. A tiny difference in the firing of a single neuron could, if the system is on the edge of chaos, make large and essentially unpredictable change in the system output.

I've finally decided to read James Gleik's Chaos book. Isn't it the case that chaos is still a deterministic system, it's just that the interactions are so complex (most non-linear) that prediction is incredibly difficult. But theoretically with perfect knowledge and massive computing power, we could accurately predict the weather, say, out to the limits of that computing power. Isn't that the case?

No. It's more that the sensitivity to initial conditions in even a relatively simple chaotic system is so extreme that no amount of computing power could ever predict it, even though it is governed by fully understood mathematical processes. For instance, double pendulums. The mathematical model only applies to an idealised pendulum. Its sensitivity is so extreme that the motion of a real pendulum cannot be predicted beyond the first few swings.

Are you sure that's not just a practical limitation? Theoretically with perfect knowledge it should be possible to model any deterministic system? Or is it a case of a class of unsolvable mathematical problems?

[Xamonas Chegwé]

In addition, chaos theory comes into play in complex systems like the brain, even if we stick to totally classical physics. A tiny difference in the firing of a single neuron could, if the system is on the edge of chaos, make large and essentially unpredictable change in the system output.

I've finally decided to read James Gleik's Chaos book. Isn't it the case that chaos is still a deterministic system, it's just that the interactions are so complex (most non-linear) that prediction is incredibly difficult. But theoretically with perfect knowledge and massive computing power, we could accurately predict the weather, say, out to the limits of that computing power. Isn't that the case?

No. It's more that the sensitivity to initial conditions in even a relatively simple chaotic system is so extreme that no amount of computing power could ever predict it, even though it is governed by fully understood mathematical processes. For instance, double pendulums. The mathematical model only applies to an idealised pendulum. Its sensitivity is so extreme that the motion of a real pendulum cannot be predicted beyond the first few swings.

Are you sure that's not just a practical limitation? Theoretically with perfect knowledge it should be possible to model any deterministic system? Or is it a case of a class of unsolvable mathematical problems?

And how exactly do you determine that "perfect knowledge"? Even if everything else remained constant, the friction in the hinges during one run would sufficiently change the surfaces that the second would be unpredictably different! Then consider temperature, humidity, air pressure, etc. - a change in any of which, even at their absolute limits of measurability, would also fuck up any hope of repeating the same swing. That's how sensitive chaotic systems are. Even simple ones. The weather is anything BUT simple!

[pErvinalia]

Yeah, but with perfect knowledge you would know all that. How do you determine perfect knowledge? You don't. We are talking theoretically here, not practically.

[MiM]

The limits of measurability stems from the uncertainty principle, which is part of quantum mechanics, so I'd give rEv right here. You need the unpredictability that comes from quantum effects to make a chaotic system impossible to predict, even in theory.

About rEv's original question. It would be relatively easy to take a device for measuring radioactive radiation, and set it up to give a signal to fire a gun, whenever it registers a gamma-ray. If you aim that gun at a mass of moving people, it would fire with quantum randomness. And who will get killed, will be determined by the random quantum effects of radioactive decay and the chaotic movement of a crowd.

Another example, is a plutonium bomb. The timing of the start of the chain reaction is very precise, and some random neutrons that get into the device at the wrong moment, can start the reaction too early. If the reaction starts too early, the effect of the bomb will be a lot smaller, making it a fizzle. So if a terrorist puts a Pu-bomb in Manhattan, and it fizzles because of this, then quantum random effects could save millions of lives in one go.

So yes, quantum randomness can definitely have an impact on the classical world.

[mistermack]

If you believe that energy and matter do actually exist, then a preferred frame seems to have to exist.
Just a micro-second after the start of the big bang, the whole universe was in a pinhead-sized speck.
In the frame where that speck is stationary, there is a certain quantity of energy. In any other frame, that is moving relative to the speck,

Let me stop you there. There is no other frame moving relative to that speck. That speck is the entire universe - everything - all matter, all energy, all movement, all reference frames - are within it. It makes no sense to talk about "outside" because you are talking about being outside of this universe.

That would make all frames the same.
A frame that is inside the universe can be considered moving relative to the overall universe.
I chose the speck example because it gives a clear picture of a finite universe, that can be considered as a whole.

If you are inside a balloon, you can still move relative to the balloon. There are billions of possible frames of reference in which the balloon can be considered to be moving. An infinity of frames. There is only one frame of reference in which the balloon is stationary.

[Xamonas Chegwé]

If you believe that energy and matter do actually exist, then a preferred frame seems to have to exist.
Just a micro-second after the start of the big bang, the whole universe was in a pinhead-sized speck.
In the frame where that speck is stationary, there is a certain quantity of energy. In any other frame, that is moving relative to the speck,

Let me stop you there. There is no other frame moving relative to that speck. That speck is the entire universe - everything - all matter, all energy, all movement, all reference frames - are within it. It makes no sense to talk about "outside" because you are talking about being outside of this universe.

That would make all frames the same.
A frame that is inside the universe can be considered moving relative to the overall universe.

Only if you accept a preferred frame - which is what you are attempting to demonstrate. Your argument becomes circular.

I chose the speck example because it gives a clear picture of a finite universe, that can be considered as a whole.

The universe is finite now.

If you are inside a balloon, you can still move relative to the balloon. There are billions of possible frames of reference in which the balloon can be considered to be moving. An infinity of frames. There is only one frame of reference in which the balloon is stationary.

Analogy fail. The balloon analogy for the expanding universe does not presume that anything is inside the balloon - the air inside and outside of the balloon are not a part of the universe. Rather, everything is on the surface of the balloon. That surface, however, is not 2-D but a 3-D manifold. You cannot talk about the balloon moving without referring to something outside of the balloon. The universe is expanding but it is not moving - not relative to anything inside of it.

[Brian Peacock]

http://www.bbc.co.uk/news/science-environment-30491840

Pretty much every thunderstorm produces a burst of gamma radiation. So why aren't there more Hulks about? Answer that one, Darwin!

Because technically those are X-rays, not gamma. If they are called gamma-ray bursts, that would be because astronomers still confuse the two, by referring to fenomena that produce highly energetic X-rays, for gammabursts. I see no reason, why this confusion should be brought back here to planet earth.

And no-one has ever seen a Hulk produced by mere X-rays

If they have a frequency above 1019 Hz, then they are gamma rays, whatever their source...

Maybe back when you went to school, but not anymore . Distingushing gamma and x-rays by source is the only sane way to distinguish them, as dividing them by frequency is completely arbitrary. But I do agree, that we would need a word for high energy photons, that would cover both .

Hulkons?

[mistermack]

If you are inside a balloon, you can still move relative to the balloon. There are billions of possible frames of reference in which the balloon can be considered to be moving. An infinity of frames. There is only one frame of reference in which the balloon is stationary.

Analogy fail. The balloon analogy for the expanding universe does not presume that anything is inside the balloon - the air inside and outside of the balloon are not a part of the universe. Rather, everything is on the surface of the balloon. That surface, however, is not 2-D but a 3-D manifold. You cannot talk about the balloon moving without referring to something outside of the balloon. The universe is expanding but it is not moving - not relative to anything inside of it.

I don't think it's as settled as you think. There is work going on right now in the world of cosmology to determine if the universe is spinning. They wouldn't be doing that, if it was settled that there was no possibility of an axis of rotation. Nobody has proved whether it is, or is not spinning.
But the fact that it's being researched, means that it's considered possible that there is a preferred axis, and a centre of gravity.
And if it was spinning, that would mean that there is a special frame, in which the centre of gravity of the universe is at rest.

Some people think that they have found evidence of spin:

In a study of over 15,000 galaxies by Michael Longo and co-investigators at the University of Michigan, the researchers report that spiral galaxies preferential spin clockwise or counter clockwise depending what hemisphere of the sky they are in.


DNEWS VIDEO: WHY STAR AGING MATTERS
SEE ALSO: 3-D Galaxy Map Reveals Cosmic Neighborhood
Longo sampled over 15,000 galaxies in the extensive Sloan Digital Sky Survey. The galaxies extend out to little more than 600 million light-years from Earth, less than 1/20 the distance to the farthest observed galaxies to date.

Looking northward, above the plane of our Milky Way, he found that more than half of the spirals were spinning in a counterclockwise direction in the sky. This overabundance seems small, only seven percent of the total observed galaxy sample. But the odds of it being purely due to chance are a one in a million say the researchers.

I'm not jumping on their bandwagon, just saying that the question is far from settled.
Others are attempting to detect spin by tiny variations in the motion of far distant bodies, but so far haven't been able to detect any.

But it's clear that the subject isn't settled, or people wouldn't be spending large sums trying to prove or disprove it.

Galaxies spin, stars spin, and planets spin. So, why not the whole universe? The consequences of a spinning universe would be profound. The cornerstone of modern cosmology is that the universe is homogeneous and isotropic — it has no preferred orientation and looks the same in all directions.

http://news.discovery.com/space/do-we-l ... 110708.htm
http://arxiv.org/abs/1104.2815

[Xamonas Chegwé]

As usual, you scour the web for some outlandish hypothesis that (you think) shows you are right. What you have posted is "out there" speculation and far removed from current consensus (in fact, the reviewer in the Discovery Channel site you linked to sounds rather skeptical - especially of the way that the axis of universal rotation seems to neatly dovetail with the orientation of the Milky Way...) It is also 4 years old and doesn't seem to have gained much ground in the interim.

But, it shows that someone somewhere sort of vaguely agrees with something similar to what you think you said, so ergo, your opinion is as right as anyone else's.

Personally, I will stick with the status quo on this subject, until there is proof of something better.

[mistermack]

As usual, you scour the web for some outlandish hypothesis that (you think) shows you are right. What you have posted is "out there" speculation and far removed from current consensus (in fact, the reviewer in the Discovery Channel site you linked to sounds rather skeptical - especially of the way that the axis of universal rotation seems to neatly dovetail with the orientation of the Milky Way...) It is also 4 years old and doesn't seem to have gained much ground in the interim.

But, it shows that someone somewhere sort of vaguely agrees with something similar to what you think you said, so ergo, your opinion is as right as anyone else's.

Personally, I will stick with the status quo on this subject, until there is proof of something better.

No, I didn't scour the web. That's just one example. Google spinning universe and loads of stuff comes up. That was just one example.
I pointed out that it's not proved or disproved. What it shows is that bona fide research is being done on the subject. Professor Longo of the University of Michigan is hardly what I would call a maverick, and nobody is rubbishing their work on the net.
I'll trust their opinion, because I haven't seen your qualifications.

It's not a question of whether the universe is spinning or not. It just illustrates that the science isn't settled, and whether it actually is or not, the Universe will still have a centre of gravity if it's finite.

[Xamonas Chegwé]

As usual, you scour the web for some outlandish hypothesis that (you think) shows you are right. What you have posted is "out there" speculation and far removed from current consensus (in fact, the reviewer in the Discovery Channel site you linked to sounds rather skeptical - especially of the way that the axis of universal rotation seems to neatly dovetail with the orientation of the Milky Way...) It is also 4 years old and doesn't seem to have gained much ground in the interim.

But, it shows that someone somewhere sort of vaguely agrees with something similar to what you think you said, so ergo, your opinion is as right as anyone else's.

Personally, I will stick with the status quo on this subject, until there is proof of something better.

No, I didn't scour the web. That's just one example. Google spinning universe and loads of stuff comes up. That was just one example.
I pointed out that it's not proved or disproved.

Neither is anything in science. There is no proof in anything but Mathematics. There are only theories. The better the theory fits the observed facts, the more accepted it is. Currently, the consensus is that the universe has no preferred reference frame. That is the theory that the majority of scientists working in the field of cosmology agree fits the known facts best.

What it shows is that bona fide research is being done on the subject. Professor Longo of the University of Michigan is hardly what I would call a maverick, and nobody is rubbishing their work on the net.

That some scientists think otherwise is fine. Science progresses by challenging the status quo. I am sure that Prof Longo is doing very valid work. But it is important to remember that most challenges don't overturn things. They serve instead to reinforce the current thinking by exploring dead-ends. Useful work, sure, but falling into the trap of accepting that all such hypotheses are equal in validity to accepted scientific thought is silly.

I'll trust their opinion, because I haven't seen your qualifications.

My qualifications are irrelevant. I am proposing nothing more than that the current status quo is to be given more credence than a fringe theory. People that support that view include Steven Hawking, Lawrence Krauss and many others whose qualifications are easy to check.

It's not a question of whether the universe is spinning or not. It just illustrates that the science isn't settled,

I know that science isn't settled. And it never will be. However, and as you constantly and doggedly ignore, that does NOT mean that fringe theories are to be given the same credence as the established view - not until strong evidence is provided.

and whether it actually is or not, the Universe will still have a centre of gravity if it's finite.

This is the crux of your misunderstanding. You appear to view the universe as a 3-dimensional spheroid, with a definite centre and an edge. This is NOT the consensual view of things. "Finite but unbounded" is the phrase you will come across if you read up on the shape of the universe. Start here https://en.wikipedia.org/wiki/Shape_of_the_universe